This invention relates to processes of preparing condensed polymers that are polyamides, polyimides, or polyamidimides and more specifically, it relates to processes of preparing condensed polymers that are polyamides, polyimides, or polyamidimides by reacting mixtures of polyamines and polycarboxylic acids or the like in solvents by using arylboric acids as polycondensation catalysts; processes of preparing condensed polymers that are polyamides, polyimides, or polyamidimides by reacting mixtures of polyamines and polycarboxylic acids or the like by using pentamethylbenzene as a solvent in the presence of polycondensation catalysts; and processes of preparing condensed polymers that are polyamides, polyimides, or polyamidimides by reacting mixtures of polyamines and polycarboxylic acids or the like by using m-terphenyl as a solvent in the presence of polycondensation catalysts.
Polyamides, with amide bonds in their principal chain, are used as fiber materials in great quantity due to their excellent frictional resistance, elasticity, chemical resistance, and dyeability. Further, they are used not only for parts of various machines and electronics, but also for films due to their excellent mechanical, abrasion-resistant, thermo-tolerant and oilproof properties, and their low coefficient of friction. Polyimides, with imide bonds in their principal chain, are one of most heat-resistant plastics, and are used for those parts of products on which high reliability is required such as airplanes, transportation, machines, and electric or electronic machines. Polyamideimides, with amide and imide bonds in their chain, are used for various molded materials.and insulating varnish because these are excellent in workabilities and abrasion resistance. The following several processes have been proposed to prepare these polyamides, polyimides, and polyamideimides.
In Japanese Laid-Open Patent Publication No. 49-106597, there is disclosed a process of preparing a macromolecular aromatic polyamide by thermal polycondensation of an aromatic diamine and an aromatic dicarboxylic acid diester, or an aromatic aminocarboxylic ester without solvent by using at least one compound of silicon, germanium, tin or lead as a polycondensation catalyst.
In Japanese Laid-Open Patent Publication No. 59-8728, there is disclosed a process of preparing an aromatic polyamide by thermal polycondensation of an aromatic aminocarboxylic acid and/or a mixture of aromatic dicarboxylic acid and an aromatic diamine in a polar solvent in the presence of a dehydration catalyst at a temperature of about 160xc2x0 C. or over.
In Japanese Laid-Open Patent Publication No. 61-14219, there is disclosed a stable process of preparing a polyamide and/or a polyamide acid which can be easily polycondensed, by using a sulfolane containing substantially no sulfolene and/or isopropylsulfolanylether as a solvent in the process of preparing a polyamide and/or polyamide acid by reacting one or more polyvalent carboxylic acids and one or more diisocyanates in the presence of one or more catalysts selected from alkali metal hydroxides, alkali metal carbonates, and alkali metal hydrogencarbonates.
In Japanese Laid-Open Patent Publication No. 8-333450, there is disclosed a process for preparing a polyimide which is stable in dimension with little residual solvent, by thermally and chemically imidising a polyimide precursor which is produced by reacting in a mixed solvent of two or more solvents selected from water soluble ether compounds, water soluble alcohol compounds, water soluble amid compounds, water soluble ketona compounds, and water, a specific aromatic diamine compound and a tetracarboxylic acid dianhydride.
In Japanese Laid-Open Patent Publication No. 8-302015, there is disclosed a polymide with a specific molecular weight and a specific structural unit, which dissolves in organic solvents having a wide range of boiling points with high solvency, is excellent in molding workabilities, and has excellent thermal resistance in spite of its softening temperature, and is useful for varnish, modling products and the like.
In Japanese Laid-Open Patent Publication No. 8-239470, there is disclosed a process of preparing a water- and oil-repellent and heat-stable polyimide resin with low surface free energy and high glass transmission temperature by reacting a specific aromatic diamine and a specific aromatic tetracarboxylic acid dianhydride.
In Japanese Laid-Open Patent Publication No. 57-133126, there is disclosed a process for preparing a polyamideimide by polycondensing a tribasic acid anhydride and a diisocyanate compound in the presence of a tertiary amine catalyst in a sulfolane solvent.
In Japanese Laid-Open Patent Publication No. 62-297329, there is disclosed a process of preparing an aromatic polyamideimide by thermal polycondensation of an aromatic tricarboxylic acid and/or aromatic tricarboxylic acid anhydride and an aromatic diamine in the presence of a dehydration catalyst and a solvent, wherein a compound selected from the group consisting of nitrobenzene, o-nitrotoluene, and benzonitrile is used as the solvent.
The present inventors, on the other hand, reported that arylboric acids with electron-withdrawing groups such as 3,4,5-trifluorophenylboric acid and 3,5-bis(trifluoromethyl)phenylboric acid can be catalysts in amide condensation of carboxylic acids and amines. (J. Org. Chem. 61, 4196-4197, 1996)
An object of the present invention is to provide processes of preparing polyamides, polyimides, and polyamineimides, which are easy to purify after the reaction, and especially aromatic polyamides (aramids), aromatic polyimides, and aromatic polyamideimides, which are said to be difficult to synthesize by direct polycondensation reactions from polyvalent carboxylic acids and polyvalent amines with high yield and without side reactions such as a change in color to black.
As mentioned above, the present inventors have already reported that arylboric acids can be a catalyst in the amide condensation of carboxylic acids and amines. In the case of polycondensation reactions where arylboric acids are used as a catalyst to prepare polyamides, it is important to select an appropriate solvent in polycondensation reaction system because the polymerization will not proceed unless trimers and dimers produced by the polycondensation are dissolved in the solvent. The inventors found a process of preparing polyamides, especially aromatic polyamides (aramids), which are said to be difficult to synthesize by direct polycondensation reactions, with high yield by direct thermal polycondensation reactions by employing combinations of the arylboric acids and appropriate solvents, and completed the present invention. The inventors also found that there are no side reactions accompanying a change of color to black when the direct polycondensation reactions of aromatic polyamides are performed at 200xc2x0 C. or over using pentamethylbenzene or m-terphenyl as solvents, and completed the present invention.
Polyamides, polyimides, and polyamideimides are examples of the condensed polymers in the processes of preparing condensed polymers where polycarboxylic acids and polyamines, polycarboxylic acids, polyamines and aminocarboxylic acids, or aminocarboxylic acids are reacted in solvents in the presence of arylboric acids as polycondensation catalysts of the present invention, or where polycarboxylic acids and polyamines, polycarboxylic acids, polyamines and amiocarboxylic acids, or aminocarboxylic acids are reacted in the presence of polycondensation catalysts in pentamethylbenzene or m-terphenyl as solvents of the present invention. Examples diamines, semiaromatic polyamides-produced from aromatic dicarboxylic acids and aliphatic diamines, or aliphatic dicarboxylic acids and aromatic diamines.
The polycarboxylic acids used in the present invention can be any of those having two or more carboxyl groups within a molecule. Dicarboxylic acids includes fumaric acid, malonic acid, adipic acid, terephthalic acid, isophthalic acid, sebacic acid, dodecanedioic acid, diphenylether-4,4xe2x80x2-dicarboxylic acid, pyridine-2,6-dicarboxylic acid or the like. Tricarboxylic acids includes butane-1 2,4-tricarboxylic acid, cyclohexane-1,2,3-tricarboxylic acid, benzene-1,2,4-tricarboxylic acid, naphthalene-1,2,4-tricarboxylic acid or the like. Tetracarboxylic acids includes butane-1,2,3,4-tetracarboxylic acid, cyclobutane-1,2,3,4-tetracarboxylic acid, benzene-1,2,4,5-tetracarboxylic acid, 3,3xe2x80x2,4,4xe2x80x2-benzophenone tetracarboxylic acid, 3,3xe2x80x2,4,4xe2x80x2-diphenylether tetracarboxylic acid or the like. Normally, dicarboxylic acids, tetracarboxylic acids, and tricarboxylic acids are used to prepare polyamides, polyimides, and polyamideimides, respectively. The polycarboxylic acids can roughly be classified into aliphatic polycarboxylic acids such as fumaric acid and cyclohexane-1,2,3-tricarboxylic acid, and aromatic polycarboxylic acids such as terephthalic acid.
The polyamines used in the present invention can be any of those having two or more amino groups in a molecule. Diamines include diaminobutane, hexamethylenediamine, trimethyl hexamethylenediamine, m-xylilenediamine, p-phenylenediamine, m-phenylenediamine, toluylenediamine, 4,4xe2x80x2-diaminodiphenylmethane, 4,4xe2x80x2-diaminodiphenylether, 3,4xe2x80x2-diaminodiphenylether, 4,4xe2x80x2-diaminobiphenyl, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-diaminobiphenyl, 4,4xe2x80x2-diaminodiphenylsulfide, 2,6-diaminonaphtalene, 4,4xe2x80x2-bis(p-aminophenoxy)diphenylsulfone, 4,4xe2x80x2bis(m-aminophenoxy)diphenylsulfone, 4,4xe2x80x2-bis(p-aminophenoxy)benzophenophene, 4,4xe2x80x2-bis(m-aminophenoxy) benzophenophene, 4,4xe2x80x2-bis(p-aminophenylmercapto)benzophenone, 4,4xe2x80x2-bis(p-aminophenylmercapto)diphenylsulfone or the like. Triamines include 4,4xe2x80x2,4xe2x80x3-triaminotriphenylmethane, triamterene or the like. The polyamines can roughly be classified into aliphatic polyamines such as hexamethylenediamine, and aromatic polyamines such as p-phenylendiamine.
The aminocarboxylic acids used in the present invention can be any of those having a carboxylic group and an amino group in a molecule, and can be specifically exemplified as xcfx89-aminoundecanoic acid, aminododecanoic acid, p-aminobenzoic acid, m-aminobenzoic acid, 6-aminonaphtalene-2-carboxylic acid, 4-(p-aminophenoxy)benzoic acid, 3-(p-aminophenoxy)benzoic acid, 4-(m-aminophenoxy)benzoic acid, 3-(m-aminophenoxy)benzoic acid or the like.
The arylboric acids used in the present invention can be any arylboric acid as long as then can act as a catalyst in polycondensing polycarboxylic acids and polyamines, polycarboxylic acids, polyamines and aminocarboxylic acids, or aminocarboxylic acids in the presence of solvents. However, it is preferable to use phenylboric acids with electron withdrawing groups at least at one of the 3,4, and 5 positions, which can be specifically exemplified as 3,4,5-trifluorophenylboric acid, 3-nitrophenylboric acid, 3,5-bis(trifluoromethyl)phenylboric acid, 3,5-bis(trifluoromethyl)phenylboric acid, and 4-trifluoromethylphenylboric acid. Among these, 3,4,5-trifluorophenylboric acid is the most desirable one in view of yield. Electron withdrawing groups can be exemplified as xe2x80x94CF3, xe2x80x94F, xe2x80x94NO2, xe2x80x94CN, xe2x80x94+NH3, xe2x80x94CHO, xe2x80x94COCH3, xe2x80x94CO2C2H5, xe2x80x94CO2H, xe2x80x94SO2CH3, xe2x80x94SO3H and the like. The arylboric acids used as polycondensation catalysts in the present invention are particularly advantageous in commercial working because they are stable, and can be easily retrieved.
As a polycondensation catalyst in the process of preparing condensed polymers by reacting polycarboxylic acids and polyamines, polycarboxylic acids, polyamines and aminocarboxylic acids, or aminocarboxylic amines in the presence of polycondensation catalysts by using pentamethylbenzene as a solvent in the present invention, it can be any of those capable of catalyzing polycondensation reaction of those starting materials in the presence of solvents containing pentamethylbenzene. As a polycondensation catalyst in the process of preparing condensed polymers in reacting polycarboxylic acids and polyamines, polycarboxylic acids, polyamines and aminocarboxylic acids, or aminocarboxylic acids in the presence of polycondensation catalysts by using m-terphenyl as a solvent in the present invention, it can be any of those usable as a catalyst in polycondensing those starting materials in the presence of solvents containing m-terphenyl. Apart from arylboric acids such as 3,4,5-trifluorophenylboric acid mentioned above, various boron compounds, phosphorus compounds, and heteropolyacids can be used as well.
Phosphorus compounds can be exemplified as phosphites such as trimethyl phosphite, triethyl phosphite, tributyl phosphite, triphenyl phosphite, tricresyl phosphite, tricyclohexyl phosphite, diethyl phosphite, diphenyl phosphite, and o-methyl-s,sxe2x80x2-diphenyl dithiophosphite; phosphates such as tributyl phosphate, triphenyl phosphate, ethylphenyl phosphate, and ethylenephenyl phosphate; phosphoric acids such as phosphoric acid, pyrophosphoric acid, methaphosphoric acid, tetrapolyphosphoric acid, trimethaphosphoric acid, and ethylmetaphosphoric acid; phosphonic acids such as phenylphosphonic acid; phosphines such as triphenyl phosphine and trioctyl phosphine; phosphine oxides such as triphenylphosphine oxide, and 1-phenylphospholine-3-oxide; and other compounds such as phosphorus pentoxide, ammonium dihydrogenphosphate, p-diethyltrimethylsilylphosphate, N,Nxe2x80x2,Nxe2x80x3-hexamethylphosphorus triamide, tetrabutylpyrophosphite, phenylphonus acid, tetrakis-(2,4-ditertiarybutylphenyl)-4,4xe2x80x2-biphenylene diphosphonite, distearyl pentaerythritol diphosphite.
As for a solvent in the process of preparing condensed polymers by reacting polycarboxylic acids and polyamines, polycarboxylic acids, polyamines and aminocarboxylic acids, or aminocarboxylic acids, using arylboric acids as polycondensation catalysts in the present invention in the presence of solvents, it can be exemplified as pentamethylbenzene, m-terphenyl, xylene, cresol, toluene, benzene, ethylbenzene, 1,3,5-triisopropylbenzene, o-dichlorobenzene, 1,2,4-trichlorobenzene, cyclohexane, cyclopentane, phenol, naphthalene, 1,2,3,4-tetrahydronaphthalene (tetralin), acetophenone, benzophenone, diphenylsulfone, N-methylpyrrolidinone (N-methylpyrrolidone), N-butylpyrrolidinone (N-butylpyrrolidone), N-ethylpyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-pyrrolidone, N,N-dimethylformamide, dimethylacetoamide, hexamethylphosphoramide, dimethylsulfoxide, nitromethane, acetonitrile, pyridine, 1,3-dimethyl-2-imidazolidinone, "Ugr"-butylolactone.
Among these solvents, in polycondenseing aromatic polycarboxylic acids and aromatic polyamines, it is desirable to use pentamethylbenzene or m-terphenyl, or more preferably, a mixed solvent of pentamethylbenzene and N-methylpyrrolidinone having a weight ratio of 70:30-90:10 or a mixed solvent of m-terphenyl and N-butylpyrrolidinone having a weight ratio of 3:1-10:1.
As a solvent used in the polycondensation of aliphatic dicarboxylic acids such as adipic acid and aliphatic diamines such as hexamethylendiamine, it is preferable to use a solvent containing o-xylene. Further, it is preferable to add m-cresol to o-xylene to effectively dissolve aliphatic amides such as nylon 6,6 prepared by the polycondensation and to proceed the reaction more sufficiently. The desirable amount of the m-cresol added is 10-30 wt %, that is, it is desirable to use a 70:30-90:10 mixed solvent of o-xylene and m-cresol, especially a mixed solvent having a volume ratio of 4:1. In the case where the amount of the m-cresol added is too much, the catalytic activity may be hampered. Further, it was also found that a desirable result was obtained when pentamethylbenzene or m-terphenyl was used instead of o-xylene. As is the case of o-xylene, when using pentamethylbenzene or m-terphenyl, it is desirable to use a mixed solvent of pentamethylbenzene and m-cresol having a weight ratio of 70:30-90:10, or a mixed solvent of m-terphenyl and m-cresol having a weight ration of 70:30-90:10.
As a solvent containing pentamethylbenzene or m-terphenyl in the present invention, the solvents containing pentamethylbenzene or m-terphenyl are used in the process of preparing polyconsdensation products by reacting polycarboxylic acids and polyamines, polycarboxylic acids, polyamines and aminocarboxylic acids, or aminocarboxylic acids in the presence of polycondensation catalysts using pentamethylbenzene or m-terphenyl as a solvent. In the case where 1,3,5-triisopropylbenzene, 1,2,4-trichlorobenzene, tetralin, cresol or the like is used as solvents, the color of the reaction system turns to black. However, it will not turn to black even when it is heated up to 200xc2x0 C. by using pentamethylbenzene, and up to 300xc2x0 C. by using m-terphenyl, and the change of color will be prevented. The change of color may be attributed to some side reactions due to the fact that it also occurs in the reaction conducted under a deoxidized atmosphere.
In the case where aromatic polyamides or the like are prepared as a condensed polymer by polycondensation, it is preferable to add N-methylpyrrolidinone (NMP) to pentamethylbenzene to efficiently dissolve the product obtained by the reaction and to sufficiently proceed the polycondensation reaction. The amount of the N-methylpyrrolidinone added is preferably 10-30 wt %, that is, it is preferable to use a mixed solvent of pentamethylbenzene and N-methylpyrrolidinone having a weight ratio of 70:30-90:10, and more preferably, a 4:1 mixed solvent of them. In the case where the amount of the N-methylpyrrolidinone added is too much, the catalytic activity maybe hampered. Further, in the case where aromatic polyamides are produced as condensed polymers by polycondensation, it is preferable to add N-butylpyrrolidinone (NBP) to m-terphenyl to effectively dissolve the product obtained by the reaction and to sufficiently proceed the polycondensation reaction. The desirable amount of the N-butylpyrrolidinone added is 9-25 wt %, that is, it is desirable to use a mixed solvent of m-terphenyl and N-butylpyrrolidinone having a weight ratio 3:1-10:1, and more desirably, a 10:1 mixed solvent of them. In the case where the amount of the N-methylpyrrolidinone added is too much, the catalytic activity may be hampered. Further, when aromatic dicaroxylic acids and aromatic diamines as starting materials are large in molecular weights, the reaction becomes effective by adding more solvent without changing the ratio of a mixed solvent.
On the other hand, in the case where aliphatic polyamides etc. are produced by polycondensation, it is desirable to add m-cresol to pentamethylbenzene or m-terphenyl to dissolve the product obtained by the reaction effectively and to proceed the reaction more sufficiently. The amount of the m-cresol added is preferably 10-30 wt %, that is, it is preferable to use a mixed solvent of pentamethylbenzene or m-terphenyl and m-cresol having a volume ratio of 70:30-90:10, and more preferably, a 4:1 mixed solvent of them. In the case where the amount of the m-cresol added is too much, the catalytic activity may be hampered. Further, when the aromatic polycaroxylic acids and aromatic polyamines as starting materials are large in molecular weights, the reaction becomes effective by adding more solvent without changing the ratio of a mixed solvent.
It is preferable to conduct the polycondensation in a process of preparing condensed products in the present invention under a deoxidized atmosphere or an argon atmosphere. The deoxidized atmosphere can be achieved by conducting the reaction in the presence of an inert gas. In an argon atmosphere, it is preferable to conduct the polycondensation reaction under argon flow, and with this argon atmosphere in a reaction, the effects of dehydration and a deoxidized atmosphere can be achieved at the same time.
Further, in the case where aromatic polycarboxylic acids and aromatic polyamines are polycondensed in pentamethylbenzene as solvents, the reaction should preferably be conducted at 160-240xc2x0 C., more preferably at 200xc2x0 C., while stirring and in m-terphenyl as solvents, it should preferably be conducted at 200-300xc2x0 C., more preferably at 300xc2x0 C., while stirring. In the case where aliphatic polycarboxylic acids and aliphatic polyamines are polycondensed, the reaction should preferably be conducted at 140-200xc2x0 C., more preferably at 150xc2x0 C., while stirring. The polyamides, polyimides, and poliamideimides prepared in the processes of condensation can be purified by the previously well known processes of purification. As mentioned above, side reactions do not occur in the processes of preparation in the present invention, and therefore the products produced by the present processes can be purified more easily than those produced by the previously well known processes.